A plug valve is a type of valve that uses a cylindrical plug as a closure mechanism. The plug has a central bore that is aligned with the direction of flow when the valve is opened and misaligned with the direction of flow when the valve is closed. A plug valve can have a profile that protrudes from the side of the pipe in which the plug valve is installed. Thus, plug valves are often used as surface valves, e.g., to control flow of well fluid (e.g., drilling mud, cement, fracking fluid, or other well fluid) into the well. The plug valve relies on high pressure, e.g., pressure of the well fluid, to create a hard metal-to-metal seal. At low pressures, however, the plug valve can be prone to leaks.
Like reference symbols in the various drawings indicate like elements.